http://www.cleverscampcamp.com/camping-pad-thermarest/

Hiking/backpacking with knee and back problems?
I just returned from a camping/backpacking trip with my co-workers. I had a really great time except for a few concerns I have. I had a really tough time going uphill and downhill especially wearing a heavy pack. Also, I have some issues with my knees and back and this made it more difficult for me and I was typically lagging behind everyone else in the group and had to have someone help me in certain spots (there were only five of us). I will admit, I am a bit out of shape and this is probably a part of it, but I was wondering if anyone who has experience can give me some suggestions as to what may help aside from stretching and working out the “kinks” in my body. (I am a 35 year old male 5’10″ weighing about 215 lbs or so if that helps you any.) I was one of the oldest in the group as well. A few people at work mentioned that I should try trekking poles next time. I am also considering tossing my cheap wal-mart sleep pad and investing in a thermarest. Any other suggestions?
You might consider more training before a hike, but also many people, especially the older they get, are learning about and switching over to ultralight backpacking.
http://www.the-ultralight-site.com/index.html
http://www.speakeasy.org/~krk/travels/backpacking/intro.html
http://www.backpackinglight.com/cgi-bin/backpackinglight/index.html
http://www.rayjardine.com/ray-way/index.htm
Thermarest Trail Lite Sleeping Pad Review